1. Field of the Invention
The present invention relates to a cathodic corrosion protection method and apparatus for electrically protecting a metal structure exposed to the atmosphere from being oxidized and corroded by electrolytic moisture and dissolved oxygen.
2. Description of the Prior Art
As a protective anode and cathodic corrosion protection system for corrosion protecting a coated surface of a metal structure exposed to the atmosphere, there is an apparatus which is developed and commercialized by C. L. I. Systems, Inc. (U.S.A.).
This corrosion protection apparatus provides an effect of corrosion protection of a metal structure which is exposed to the atmosphere and protected by coating, however, it inevitably has the following four problems. These problems are:
(1) output of a control unit is controlled to an optimum DC voltage and supplied to a plurality of anodes by wiring. However, due to differences in wiring distance of anode structure, voltage of each anode is not always an optimum value. Further, if the voltage is excessively high, there may be a problem of over-corrosion protection, and if the voltage is low, corrosion protection range is narrowed. PA1 (2) While the control unit is inputted with AC 100V or AC 200V, for corrosion protection of a metal structure disposed in an explosion-proof area, the control unit and wiring are required to have explosion-proof specifications, which requires a special consideration in construction work and has a problem of sacrificed economy. PA1 (3) There is a possibility of disconnection of the corrosion protection current due to open-circuit of wiring or the like. PA1 (4) if there is no power supply of AC 100V or AC 200 V available in the vicinity, it is necessary to provide a power supply over a long distance.